Can a person with dementia who tested competent still drive?

My Mother tested 18 on a competent test. 15 is incompetent. My sisters the Trustees are saying they can do nothing about her still driving or living alone. My mother has lost 10 pounds since my last visit last year and now weighs 90 pounds. She has been more confused and her memory is getting worse. She just got back from Vegas where security had to call my sister who was in California because she didn't know where she was and forgot that she was with my Cousin. I flew to Vegas to get her and she asked me every morning where she was. She has good moments and then really confusing moments. I personally thought she should stop driving a year ago but the Trustees say because there is nothing they can do and because nothing has happened they cannot do anything. I am not a Trustess and have no power what should I do? This woman should not be on the road with her memory. Another thing is my Mother keeps accusing me of taking her Trust papers which I didn't. I saw the trust papers my last visit. Since then my 2 sisters have been to visit twice. Even in my mother's state she always puts things in the same place. There are no trust papers anywhere. It is my understanding that anytime my Mother makes changes she is suppose to get a copy and I know my sisters since my last visit made changes such as making themselves co-trustees and some other changes which my mother doesn't remember and my sisters won't tell me. I have asked my sister about this and she won't respond saying that everything is fair. Do I have a right to take my mother to the trust attorney and ask for a copy?